Basics of Open System Interconnection OSI model

Duration: 10 min

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Module outline

  1. Discrete Mathematics: Set Theory, Relations, Functions, Graph Theory, Group Theory, Propositional and Predicate Logic
  2. DataBase Management System/DBMS: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Relational Calculus, Transaction Management, Concurrency Control
  3. Digital Electronics: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation
  4. Computer Architecture: Floating Point Rep, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design
  5. Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management
  6. C Language: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  7. Data Structures: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  8. Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos
  9. Computer Networks: Introduction to CN, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware Basics
  10. Theory Of Computation/Automata Theory: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Moore & Mealy Machines, Pushdown Automata & CFG, Turing Machines, Complexity Theory
  11. Compiler Design: Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization, Run Time Environment
  12. Engineering Mathematics: Permutation and Combination, Linear Algebra, Calculus, Probability, Statistics
  13. General Aptitude: Ratio and Proportion (Ratios), Divisibility Rules, Data Interpretation, Logarithm, Number System, HCF LCM, Sequence and Series (Series), Speed Time and Distance, Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Percentage, Mensuration and Geometry, Mental Ability, Arithmetic, Profit and Loss, Powers and Exponents (Surds and Indices), Average, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Syllogisms, Venn Diagram, Seating Arrangements, Blood Relations, Directions (Direction Test), Analogy, Algebra, Time and Work, Analytical Reasoning (Counting Figures Reasoning), Puzzle Solving (Puzzles), Cubes & Dices, Ranking, Order and Sequence, Mixture and Alligation, Age Problems, Clock, Selection Decision Table (Decision Making), Data Arrangement
  14. English (Verbal Aptitude): Vocabulary, Noun, Subject Verb Agreement (Verb Noun Agreement), Adjectives, Tenses, Pronoun, Preposition, Direct and Indirect Speech, Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Sentence Completion (Fill in the blanks), Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Sentence Correction (Error Correction), Verbal Analogy (Word Based Analogy), Conjunction, Interjection, Verb, Articles, Adverb, Modals, Sentence Construction
  15. Live Classes Recordings(Earlier Batch): GATE 2026 Live Class
  16. Full Mock Test:
  17. Previous Year Papers:
  18. GATE 2026 Counselling: Counselling and Guidance Sessions
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

The lecture introduces the OSI model as a conceptual framework proposed by ISO to enable communication between heterogeneous systems. It emphasizes that the OSI model is not a protocol but an architectural reference, consisting of seven layers: Application, Presentation, Session, Transport, Network, Data Link, and Physical. The instructor uses diagrams to show encapsulation, where headers (AH, PH, SH, TH, NH, DH) are added to data as it moves down the stack, ending in bits on the media. A protocol table maps real-world protocols like TCP, UDP, IP, ICMP, ARP, and RARP to their respective layers, contrasting the OSI model as 'Directive Principles' with actual protocols as the 'Constitution'.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The slide titled 'Network Models' introduces the OSI model, noting that ISO proposed it to allow two systems to communicate regardless of architecture. A seven-layer diagram is shown alongside a staircase encapsulation model with headers AH, PH, SH, TH, NH, and DH. The instructor enters the frame to begin explaining the layered task concept.

  2. 2:00 – 5:00 02:00-05:00

    The lecture clarifies that an open system allows different systems to communicate without changing underlying hardware or software logic. A key transition occurs where the instructor states, 'The OSI model is not a protocol,' but rather a model for designing flexible and robust network architectures. A protocol table appears, mapping TCP/UDP to Transport and IP/ICMP to Network.

  3. 5:00 – 10:00 05:00-10:00

    The instructor elaborates on the seven separate but related layers, using a stylus to point at the encapsulation diagram. The diagrams are labeled 'Directive Principles' for the OSI stack and 'Constitution' for the protocol table. The slide text emphasizes that each layer defines a part of the process of moving information across a network.

  4. 10:00 – 10:02 10:00-10:02

    The final view shows the complete 'Constitution' chart mapping additional protocols like SNMP, NTP, HTTP, and FTP to their layers. The summary reinforces that the OSI model provides a standardized framework for understanding how data is encapsulated and transmitted through different system architectures.

The lecture provides a foundational overview of the OSI model, focusing on its role as an architectural reference rather than a specific protocol. Key concepts include the seven-layer hierarchy and the process of encapsulation, where data is wrapped with headers at each level. The instructor uses a metaphor comparing the OSI model to 'Directive Principles' and actual protocols like TCP/IP to the 'Constitution,' highlighting that while the model provides a standard for design, real-world implementations vary. This distinction is crucial for students to understand that the OSI model is a tool for analysis and design, ensuring interoperability across different hardware and software environments.

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